There are very few mods around for RPGM games as the format is unfriendly to external modifications.
Most commercial and some hobby games are released with the files encrypted (i.e. within a xp3 archive or similar) and these can not be easily edited at all. The format does allow an unencrypted file to be added to the game directory and it will override the internal file, but because you are basically flying blind its very hard to see how to change things.
There are some decryption programs available but it's very version dependent and quite a bit of hassle last time I tried.
If the game is unencrypted then you can load it up into the RPGM editor with some work.
RPGM as a platform is basically not at all friendly to mods, unlike Renpy.
Converting a rpgm game to renpy would be a large task. You'd need to extract all the images (unencrypt the game first). Then extract all the dialogue. then manually put together a renpy script that recreates the scenes. The 2d-topdown rpg gameplay built-in to RPGM, with maps and movement and tactical battles and items and equipment etc etc etc would all have to be recreated in renpy (a huge task). You could throw most of that part away and replace with renpy menus ("go to Town X") to just preserve the storyline and the event graphics if you wanted, but that would be an adaption rather than a port.
Finally, you should consider the "honor amongst thieves" aspect - it's one thing to pirate a game, but a whole different one to take another developers assets and make a shitty clone.